1. Field of the Invention
The invention relates to an artificial nipple for a nursing bottle used for feeding milk to infants.
2. Description of the Related Art
Milk is fed to an infant by the infant's sucking movements, wherein an artificial nipple is squeezed from the bottom to the top by the peristalsis-like movements of the infant's tongue while the nipple is located in the sucking fossa of the infant's upper jaw. The milk is fed when the nipple is in close contact with the infant's sucking fossa.
In view of this fact, Japanese Unexamined Patent Publication No. 2000-288 proposes, to facilitate the sucking movements of infants, an artificial nipple for a nursing bottle that is capable of smoothly inserting the nipple top part inside the sucking fossa by decentering the nipple top part.
However, such an artificial nipple has problems: infants feel discomfort because the artificial nipple is different in shape from a human nipple; and, in many cases, since the nipple top part does not fit the sucking fossa, the nipple is forced into the sucking fossa, resulting in feeding failure. This is because the upper and lower parts of the nipple contact each other and the nipple is compressed flat, resulting in a vacuum in the interior of the nipple.
Japanese Patent No. 2781246 proposes an artificial nipple for a nursing bottle having a check valve for smoothly feeding a liquid drink by peristalsis-like movements. Such an artificial nipple can be formed into a shape similar to a human nipple, and the nipple top part, when made of a material with excellent elasticity, can properly enter the sucking fossa. However, there are some problems in such an artificial nipple, i.e., when the nipple top part is deformed, it inhibits smooth peristalsis-like movements; it is difficult to fit the nipple top part into the sucking fossa of the infant; and due to the slit-shaped valve opening of the check valve, when the valve opening is closed, the interior of the nipple becomes a vacuum, resulting in feeding failure.